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MED-EKG
User Manual
Rev. 1.0
Freescale Semiconductor Inc.
Contents
1 Overview ......................................................................................................................................................3
2 Reference Documents ..............................................................................................................................4
3 Hardware Features ...................................................................................................................................4
3.1 System Power ....................................................................................................................................................................... 4
3.2 Debug Interface ................................................................................................................................................................... 4
3.3 Medical Connector.............................................................................................................................................................. 4
3.4 Mechanical Form Factor .................................................................................................................................................. 5
3.5 External Electrodes Connector ..................................................................................................................................... 5
3.6 Slider Electrodes ................................................................................................................................................................. 6
4 Jumper Table ..............................................................................................................................................6
MED-EKG User Manual
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1 Overview
The Medical EKG Module (MED-EKG) is a low cost development board that allows users to rapidly
prototype electrocardiogram (EKG/ECG) applications. Users can choose to develop EKG/ECG
applications using the external analog components or by using the Flexis MM microcontroller’s on-chip
analog modules or a mixture of both. MED-EKG is designed to work with the TWR-MCF51MM module
and TWR-S08MM128 module. The EKG/ECG software demonstration and step-by-step lab guide is
available in the both the Tower System TWR-MCF51MM-KIT and TWR-S08MM128-KIT or from
www.freescale.com
NOTE: TWR-MCF51MM-KIT features the 32-bit MCF51MM256 microcontroller and the TWRS08MM128-KIT features the 8-bit MC9S08MM128 microcontroller. Peripherals between these two 32bit and 8-bit MCUs are either identical or compatible; they are called the Flexis devices.
The following list summarizes the features of the MED-EKG board:
• Freescale Tower System compliant and small form factor
• External connector to TWR-S08MM128 and TWR-MCF51MM MCU modules
• Includes the MC56F8006 DSC used for signal conditioning
• Electrodes embedded in development board for easy EKG signal detection using fingertips
• Open connector for any type of EKG electrodes for additional precision
• JTAG-ONCE connector for DSC programming
• Different jumper configurations to allow various signal conditions
• Low power
Figure 1. MED-EKG Block Diagram
Integrated
Electrodes
(left, right and
reference
sliders)
JTAG/ONCE
Low-pass
filter
Compensation
PWM
External
INA
Analog
band-pass
filter
External
amplifier
External
electrodes
connector
ADC
Internal MM
amplifiers (INA
configuration)
3.3 V
Analog
band-pass
filter
Internal
MM
amplifier
Medical Connector
14-pin header
IIC bus
1,6 V
External
amplifier
MM
12-bit DAC
Low-pass
filter
Compensation
Freescale Silicon
External Connectors
Interface Circuits
Jumper configurations INA Instrumentation Amplifier
MED-EKG User Manual
MM
16-bitADC
Internal
amplifiers
In/Out
MC56F8006
16-bit Digital
Signal Controller
Analog
notch
filter
Reference
voltage
3.3 V
Power
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2 Reference Documents
The documents listed below are available online. Refer to www.freescale.com/tower or
www.freescale.com/medical for the latest revisions of these documents.
• MED-EKG Schematics
• Quick Start Guide for TWR-S08MM128
• Quick Start Guide for TWR-MCF51MM
• TWR-MCF51MM-KIT and TWR-S08MM128-KIT Labs
3 Hardware Features
This section provides more details about the features and functionality of the MED-EKG.
3.1 System Power
The MED-EKG is powered by the default trough connector J1, but can be also powered by the JTAGONCE port. Do not apply both power sources at the same time.
NOTE: Power switch is controlled by the MCF51MM256 or MC9S08MM128 pin PTE7 from the
corresponding Tower System MCU module. To turn on the MED-EKG module in your software, make
sure to set PTE7 pin to output low (active low). To turn off, set PTE7 to output high. This has already
been done in the MED-EKG demonstration software in the TWR-MCF51MM-KIT or TWR-S08MM128KIT.
3.2 Debug Interface
The included DSC is factory programmed with firmware for digital filtering (a band-pass filter and a
notch filter), however it can be reprogrammed using an external JTAG-ONCE interface (USB-TAP) for
user specific applications. It can be connected on header J10.
3.3 Medical Connector
Header J1 (2x10 pins) of MED-EKG provides connectivity with either the TWR-MCF51MM or the TWRS08MM128 board through the medical connector. It allows the use of internal OPAMPs, TRIAMPs, ADC
and DAC of Flexis MM 32-bit or 8-bit microcontrollers to implement the requirement of signal
conditioning. Pin 3 and 4 can also be used to send DSC filtered data to the target Tower MCU. Table 1
shows the signal present in each pin of medical connector. Please refer to TWR-MCF51MM-KIT or the
TWR-S08MM128-KIT LAB1 MED-EKG DEMO for instructions on assembling with the Tower System.
MED-EKG Signal
VDD(3.3V)
ECG_IIC_SDA
MM_AdcEcgSignal
MM_AdcBaseline
OUT1
Pin
1
3
5
7
9
2
4
6
8
10
MED-EKG Signal
GND
ECG_IIC_SCL
GND
MMDac
OUT2
MED-EKG User Manual
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INP1INP1+
VINP1
VINN1
TRIOUT1
11
13
15
17
19
12
14
16
18
20
INP2INP2+
VINP2
VINN2
TRIOUT2
Table 1. Medical Connector 2x10 Pin Header Connections
3.4 Mechanical Form Factor
The MED-EKG is intended to be used as an expansion of the TWR-S08MM128 and TWR-MCF51MM
boards. It’s designed for the Freescale Tower System and complies with the electrical and mechanical
specifications that are described in Freescale Tower Electromechanical Specification.
3.5 External Electrodes Connector
The external electrodes connector is labeled as J12 on the MED-EKG module. This connection yields
less noise and provides the best way to prototype your EKG application instead of using the on-board
sliders contact. The user can connect a 3 lead cable (2 electrodes and 1 ground) via J12 header and use
external electrodes. Freescale does not provide this lead due to regulations in different countries. The
user has to purchase it separately. This board was tested with Welch Allyn ECG Lead Wires for Atlas
Monitor, 3-lead AHA. Figure 2 shows a connection example with external electrodes.
Figure 2. External Electrodes Connection Example
MED-EKG User Manual
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3.6 Slider Electrodes
The on-board slider electrodes are used when external electrodes are not available. The user can place
their fingers as is shown in Figure 3. Since the contact is not as secure as the external electrodes leads,
you must avoid any small movement to reduce input noise. See TWR-MCF51MM-KIT or TWRS08MM128-KIT LAB1 guide for tips.
Figure 3. Fingertips Collocation on Slider Electrodes
4 Jumper Table
There are several jumpers provided for configuration and connection selection. Refer to Table 2 for
details. The default installed jumper settings are shown in bold.
Jumper
Option
J1
Medical board connector
J2
Connection of MM
OPAMP2 INP2-
J3
Right electrode gain (must be
the same as J4)
J4
Left electrode gain (must be the
same as J3)
J5
Enabling R17 connection
J6
Right electrode connection
(must be the same as J7)
J7
Left electrode connection (must
be the same as J6)
J8
ADC input to DSC
Setting
Description
Connection with TWR-S08MM128 or TWR-MCF51MM
open
boards
1-2 Directly to Vref1.6V
2-3 Trough R12 to OUT2
1-2 Gain is 100x
2-3 Gain is 10x
1-2 Gain is 100x
2-3 Gain is 10x
open R17 connection is open
shunt R17 is connected to Vref1.6V
1-2 Right electrode is connected to external INA input
2-3 Right electrode is connected to MM internal amplifiers
1-2 Left electrode is connected to external INA input
2-3 Left electrode is connected to MM internal amplifiers
1-2 DSC is feed from internal MM amplifiers output
2-3 DSC is feed from signal selected in J9
MED-EKG User Manual
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J9
Signal selector jumper
J10
JTAG-ONCE header
J11
Reference electrodes selector
J12
External electrodes connector
1-2
2-3
open
1-2
2-3
open
Selected signal is the external INA circuit
Selected signal is the output of internal amplifier OUT2
It is used to program the DSC
Reference electrodes are connected to ground
Reference electrodes are connected to Vref1.6V
It is used to connect external electrodes
Table 2. MED-EKG Jumper Table
NOTE: When J3 and J4 are set to 100x, you must use external electrodes via J12 instead of using the
on-board slider contacts. On-board slider contacts yield more noise due to the unsecure connection
with fingers. Noise in the first stage of instrumentation with higher amplification can easily results with
saturated output so you won’t be able to see the EKG output in the final amplification stage.
NOTE: MEG-EKG by default is configured to use the Flexis MM on-chip analogs. The option that uses
external INA is not functional by default.
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MED-EKG User Manual
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